My 3 1/2 Year Old Night Owl.

Put him to bed much, much earlier. There is a window where they will fall asleep; adrenaline will kick in if he's put down after that window.

Start the whole routine of winding down around 6:45/7. Kids that age still need between 11 & 12 hours of sleep. Esp if he's letting go of naps, more sleep at night is required.

His nap may be a tad late, you could try upping the time he goes down and waking him by 2. Or he could be outgrowing it and this could be impacting his ability to go to sleep at night.

Make sure he's getting enough physical exercise to be tired enough to sleep. The Pajanimals DVD called "Good Night, Pajanimals!":
http://www.amazon.com/Pajanimals-Good-Night/dp/B002YE26MA
has a song called "Jiggle, Jumble and Jump" and talks about getting yourself tired so you can sleep, very cute bedtime DVD for kids. I take my guy out for some running and jumping before he gets his bath and relax time.

And, you might consider giving him a snack that can help him relax and sleep about an hour before bedtime, before you start his wind down/relax routine. A bowl of oatmeal with a little milk, a banana and a small cup of milk, or a banana smoothie (banana, a little milk and some ice,) cottage cheese and crackers, yogurt, or a small serving of low-fat ice cream all contain melatonin and seratonin to help him sleep, works for grown-ups, too❤

START the bedtime routine, EARLIER.
Not AT bedtime.
You have to, factor in the time it takes to prep for bed... not doing it AT bedtime, bur PRIOR to bed time.
Otherwise, everything will get later.

Kids, this age and older, need to WIND-down first, before bed. My kids, I do that 1 hour PRIOR to bed time.
So their bedtime is still, on time.
Make the house quiet and dark... for winding-down. NO horse-play before bed. That just keys them up, and sabotages them being able to key down and to wind-down, before bed.

BOTH my kids, have always, since baby-hood, wake up in the morning before 7:00am. It is just the way they are.
And per school, I wake them up, in order to get ready, on time.

2) Kids, this age also dream and have night-mares and wake. It wakes them. Sometimes they can go back to sleep. Sometimes not.
It happens.

I just went through that very icky period. My son would nap at preschool, go to bed at 8, then stay up talking to himself for well over an hour every night. On the weekends he'd miss his nap and be grumpy around bedtime but fall asleep quickly. Now he's out of school for the summer and we're skipping the nap altogether and it's been going really well. He falls asleep quickly and doesn't seem too grumpy in the evenings anymore. He'll be 4 next month. I know most kids drop the nap a little later, but his one of those kids who's always just seemed to need the minimum amount of recommended sleep- maybe yours is the same. And honestly, I love the freedom of not having to be home for that afternoon nap/battle. we have started a "rest time" in the afternoon- he can play quietly or sometimes I;ll let him watch a show while he lies down. That seems to re-energize us both and he sees it as a treat/ compromise for not having to nap. Maybe your son will be ready to drop the nap soon as well.

Some kids don't require as much sleep as others. Your son may be one of those. My youngest son had given up napping by the age of 3 and would then go to bed about 8 and sleep all night. If by chance he did take a nap there was no way he would fall asleep by 8 and sleep all night. His older brother on the other had napped until he was 6 and would still fall asleep by 7 or so each night. They are still somewhat that way at 18 and 23.

It would be beneficial for you to google "moxie 3 year old sleep" and click on the first link. Reading the discussion will help you understand potential reasons for your son's sleep, as well as help you feel better that he has not 'broken' in some way (which is how I often feel when my children's sleep changes for the worse). One of your responders said kids at this age still need 11-12 hours of sleep per night. That may be true for most kids, but don't forget that kids vary more widely than that in their needs.

I struggled with the same thing. Alex was a nightmare with no nap, but if he napped he would not go to bed until super late and then he would turn around and wake early in the morning....OR we will have a busy day and he will go to bed early ( 8-9ish) and then wake up at say midnight like he is ready to face a new day.
I wish I had advice. MY situation is a tad different, Alex is on the spectrum and I guess kids who fall on the spectrum require less sleep.
I think at 3 and 1/2 he may be ready to go off his nap and then maybe you can get him on an earlier bedtime.
Alex is 4 and no longer naps.
You are so lucky that he is getting up to go potty in the night = )

My daughter could not take naps. If she took a nap she was up to midnight. Yet would still wake up at 5am. We stopped the naps and instead had downtime. Put on a disney movie or some quiet music and just chill out for a hal hour or so. Rested her enough. We would start bed at 8 with a nice bath pjs and into bed. Then it was story time. Sometimes is she was a bit restless we'd put disny on for jsut a bit. By 9 she was sleeping happily. It has to become a routine though. Every night for a while.